which is the energy for one photon, then can you see what the energy of many photons is??

[tex]E=nh\nu[/tex]

where n is the number of photons, hence rearrage to get n,

i presume the photons get diffracted as they go through the hole in which case

[tex] E=\frac{nhc}{\lambda}[/tex]

where lambda is
[tex]\lambda=2d\sin\theta[/tex]

because you haven't given information on what you are given ie what values you have, I will also give you this for a particle,

[tex]E=\frac{n\hbar^{2}k^{2}}{2m}[/tex]

where

[tex]k=\frac{2\pi}{\lambda}[/tex]

and as before [tex]\lambda=2d\sin\theta[/tex]

also when asking questions, it is best to put more into them, your own workings and understanding and also a bit more in about the question, it is not easy to understand what you are asking with only 2 lines of writing